Final answer:
Genetic drift is a random change in allele frequencies that occurs in a small population. An example is a population of cats with different allele frequencies for the size gene. If only a few individuals reproduce, the gene pool may shift and potentially eliminate certain alleles over time.
Step-by-step explanation:
Genetic drift is a random change in allele frequencies that occurs in a small population. For example, imagine a population of cats where the gene for size has two alleles: big (B) and small (b). In the first generation, both alleles occur with equal frequency, so p=q=0.5. If only a few individuals reproduce, by chance most of the reproducing alleles may be of the big (B) allele, causing the gene pool to shift towards bigger individuals in the second generation, and potentially eliminating the small (b) allele over time.